/Engine/Source/Runtime/Engine/Classes/Animation/AnimCompress.h
Common compression utility to retain only intermittent rotation keys. For example, calling with an Interval of 3 would keep every third key in the set and discard the rest
static void FilterIntermittentRotationKeys ( struct [FRotationTrack](API\Runtime\Engine\Animation\FRotationTrack) & Track, int32 StartIndex, int32 Interval )